Exemplary embodiments of the invention relate to navigational and sensing systems, and more particularly, to an over the horizon sensor system for a ship or stationary ground base.
Radar, or radio detection and ranging, typically involves the transmission of electromagnetic energy through the atmosphere to an area of interest. The electromagnetic energy is reflected by objects in the area of interest and the reflections are analyzed to determine the object's type, range and direction. Two parameters of a radar system's performance that are of particular interest are the maximum range at which objects can be detected and the resolution that can be located and tracked once detected. Over the horizon radar systems commonly used on ships employ antennas and transceivers on masts to detect objects beyond the visual horizon. However, the sensing range and resolution of an over-the-horizon system are limited by the height of the system antenna.
Similar conditions exist when utilizing an EO, or electro-optical, sensing device to examine objects of interest over a distance, either on a ship or at a stationary, ground location. Instead of transmitting electromagnetic energy through the atmosphere to an area of interest, electro-optical sensors gather electromagnetic energy being transmitted from objects in the environment, analyzing these signals to determine an object's type, range and distance. The maximum range at which objects can be detected and the resolution they can be detected at are also parameter's of a electro-optical sensor's performance, limiting such sensors in most cases to investigation of line-of-sight areas. Ships and ground based systems often employ towers or masts to increase the sensing height of these electro-optical sensors, thus increasing their range of sensing.
A lighter-than-air device or rotary wing aircraft may be used to improve the sensing range of navigational and detection systems of a ship or ground-based sensing platforms. However, the range of the sensing system is only improved when the lighter-than-air device or vertical lift aircraft is at an altitude above the antenna of the ship or existing infrastructure or terrain features. Because conventional vertical lift aircraft have a limited fuel capacity, they may remain airborne for only a short period of time, such as a few hours for example. Therefore the improvement in the range of the navigational and detection systems is only temporary. Lighter-than-air devices may remain aloft for extended periods of time. However, lighter-than-air devices are made from relatively thin materials and therefore are more susceptible to wind and other weather effects which limit operation thereof. Consequently, lighter-than-air devices are more susceptible to failure and such failures are more commonly catastrophic.
Likewise, both lighter-than-air devices and conventional vertical lift aircraft are limited in their ability to further explore an area of interest or prosecute a target identified at a distance. Because of their limited fuel capacity, a conventional vertical lift aircraft may only remain airborne for a short period of time, limiting its effective ability to travel to an area of interest, explore further, and then return to a safe landing location. The slow speed of a lighter-than-air device renders them ineffectual at close exploration, as most often a target of interest will have moved or changed significantly in the time a lighter-than-air device would take to transit to the region.